Travelers will soon face restrictions on how many portable chargers they can carry on a flight as airlines continue to try to reduce the risk of another lithium battery fire aboard their jets.

Southwest Airlines announced Tuesday that starting April 20 passengers will only be able to carry one charger on their planes, and they won’t be allowed to put it in the overhead bin or in their checked luggage. The airline already requires passengers to keep their chargers in the open while they are using them, so flight attendants can act quickly if they start to overheat.

The new Southwest rule goes even further than the limit of two chargers per passenger that the International Civil Aviation Organization recommended last month. But the airline says it isn’t going to aggressively enforce the policy by searching bags and confiscating chargers. Instead, Southwest’s Vice President of Safety and Security Dave Hunt said the airline will stress this to travelers when they book their flights and arrive at the airport while explaining the potential dangers.

That alone might be a big help because most people don’t seem to be aware of the risks, said Jeff Marootian, who is CEO of UL Standards & Engagement, which establishes the guidelines for the makers of these chargers and other electronic devices.